Delphi XE2 VCL样式，如何从TLabel中删除样式或禁用类皮肤？

Question

使用XE2 VCL样式，我希望禁用TLabel的皮肤效果（或属性sfTextLabelNormal）。

我尝试了其他问题中提供的各种解决方案，例如使用Engine.UnRegisterStyleHook，但没有效果。

- hikari

---

用TPaintbox自定义绘制可能会比替换TLabel稍微更省力。 - Warren P

Answer 1

TLabel组件不使用样式钩子，因为它不是TWinControl的后代类，所以你不能使用UnRegisterStyleHook函数。相反，你必须重写Paint方法的DoDrawText方法。

更新：

这里有一个如何覆盖 TLabel 组件的绘制过程的示例。

//declare this code in the implementation part 
uses
 Vcl.Themes,
 Vcl.Styles;

type
  TLabelHelper= class helper for TCustomLabel
    procedure DrawNormalText(DC: HDC; const Text: UnicodeString; var TextRect: TRect; TextFlags: Cardinal);
  end;

{ TLabelHelper }

procedure TLabelHelper.DrawNormalText(DC: HDC; const Text: UnicodeString;
  var TextRect: TRect; TextFlags: Cardinal);
begin
  Self.DoDrawNormalText(DC, Text, TextRect, TextFlags);
end;


{ TLabel }

procedure TLabel.DoDrawText(var Rect: TRect; Flags: Integer);
const
  EllipsisStr = '...';
  Ellipsis: array[TEllipsisPosition] of Longint = (0, DT_PATH_ELLIPSIS, DT_END_ELLIPSIS, DT_WORD_ELLIPSIS);
var
  Text, DText: string;
  NewRect: TRect;
  Height, Delim: Integer;
begin
  Text := GetLabelText;
  if (Flags and DT_CALCRECT <> 0) and
     ((Text = '') or ShowAccelChar and (Text[1] = '&') and (Length(Text) = 1)) then
    Text := Text + ' ';

  if Text <> '' then
  begin
    if not ShowAccelChar then Flags := Flags or DT_NOPREFIX;
    Flags := DrawTextBiDiModeFlags(Flags);
    Canvas.Font := Font;
    if (EllipsisPosition <> epNone) and not AutoSize then
    begin
      DText := Text;
      Flags := Flags and not DT_EXPANDTABS;
      Flags := Flags or Ellipsis[EllipsisPosition];
      if WordWrap and (EllipsisPosition in [epEndEllipsis, epWordEllipsis]) then
      begin
        repeat
          NewRect := Rect;
          Dec(NewRect.Right, Canvas.TextWidth(EllipsisStr));
          DrawNormalText(Canvas.Handle, DText, NewRect, Flags or DT_CALCRECT);
          Height := NewRect.Bottom - NewRect.Top;
          if (Height > ClientHeight) and (Height > Canvas.Font.Height) then
          begin
            Delim := LastDelimiter(' '#9, Text);
            if Delim = 0 then
              Delim := Length(Text);
            Dec(Delim);
            if ByteType(Text, Delim) = mbLeadByte then
              Dec(Delim);
            Text := Copy(Text, 1, Delim);
            DText := Text + EllipsisStr;
            if Text = '' then
              Break;
          end else
            Break;
        until False;
      end;
      if Text <> '' then
        Text := DText;
    end;

    if Enabled or StyleServices.Enabled then
      DrawNormalText(Canvas.Handle, Text, Rect, Flags)
    else
    begin
      OffsetRect(Rect, 1, 1);
      Canvas.Font.Color := clBtnHighlight;
      DrawNormalText(Canvas.Handle, Text, Rect, Flags);
      OffsetRect(Rect, -1, -1);
      Canvas.Font.Color := clBtnShadow;
      DrawNormalText(Canvas.Handle, Text, Rect, Flags);
    end;
  end;
end;

在使用之前，需通过以下方式声明一个interposer类

  TLabel = class (Vcl.StdCtrls.TLabel)
    procedure DoDrawText(var Rect: TRect; Flags: Longint); override;
  end;

这就是结果

- RRUZ

---

你能给我一个覆盖它的例子吗？只保留字体颜色等就足够了。谢谢。 - hikari

我遇到了与上述相同的问题，这个解决方案既优雅又简约，所以我给它点赞 =] - Kieran Wilson

这个救了我的命:D - Jerry Dodge

@hikari，此答案是在StyleElements属性尚未引入时制作的。使用新版本的Delphi，您只需要使用此属性来禁用TLabel的样式。因此，只需删除此属性的SeFont元素，TLabel将使用定义的自定义颜色。 - RRUZ

Answer 2

对 RRUZ 的解决方案进行了一些修改（完整组件，少写一些）：

type
    TjsLabel = class(TLabel)
    private
      FDisableTheme: Boolean;
      procedure SetDisableTheme(const Value: Boolean);
    protected

    public
      procedure Invalidate;override;
    published
      property DisableTheme:Boolean read FDisableTheme write SetDisableTheme;
    end;


procedure Register;

implementation
uses Themes, Styles;

type
    TLabelHelper = class helper for TCustomLabel
      procedure SetThemeBehavior(const AEnableTheme:Boolean);
    end;

    procedure Register;
    begin
      RegisterComponents('JS', [TJSLabel]);
    end;


    procedure TJSLabel.Invalidate;
    begin
      SetThemeBehavior(not DisableTheme);
      inherited;
    end;


    procedure TJSLabel.SetDisableTheme(const Value: Boolean);
    begin
      if FDisableTheme <> Value then
      begin
        FDisableTheme := Value;
        SetThemeBehavior(not Value);
      end;
    end;

    { TLabelHelper }

    procedure TLabelHelper.SetThemeBehavior(const AEnableTheme: Boolean);
    begin
      Self.FDrawTextProc := Self.DoDrawNormalText;
      if AEnableTheme then
        if StyleServices.Enabled then
           Self.FDrawTextProc := Self.DoDrawThemeTextEx
    end;

- stoklosa